I cant think of any but the splitfire sparkplugs I have in my 91 RS that could be causing my detonation. So how can I tell hot of a plug is in it? Thanks.

 

You would have to reference the part number to a splitfire book to see. It used to be that there were almost no heat range choices available for those crap plugs, now theres more but its limited.

I would run stock AC plugs if I were you.